Router bit



A. W. COCHRAN ROUTER BIT 7M 7 m a I! d 4 up 3 Patented Feb. 19, 1929. I v 1 l 7 l UNITED srATas j ALBERT WJGOCHRAN, OFQPORTLAND, on'neon;

' ROUTER 3n.- 7

Application filed July 13, 1 .9 25. Serial Nd. 43;2 84.

I My inventionrelates to router bits of the type used to remove non-printing surfaces of stereotype plates and the like.

Heretofore, a single bladed router -bitw'as,

generally used, thesingle bladebeing carried oif-center on the shank. A single-bladed router bit has this disadvantage: It imposes a relatively large off-center loadupoii. the

shank, and thus, imposes a relatively great this manner, cutequally on both sides of the :7 center line, thus: producing no off-center load twisting strain, which requires that the shank and the blade bemade extra thick soa's to router-bit not subject/to said draw-backs. To

this end my improved router-bit is provided with two blades, of substantially equal size and shape and arrangeddiametrically opposite each other on opposite sides of the center line of the shank. The blades arranged in thereon.

A further object of my invention is to provide' a router-bit with a relatively thin blade pack tight about the bit to tend to jambthe This object is "at-.,

so as to permit it to enter the work more eas-f ily.- I attain this object by making the blades of progressively decreasing thickness from the portion adjacent the shank, to the cutting edge at the extremity of said blade. That is,

the cutting'edge is the thinnest. portion of the blade and it is progressively thicker towards theshank portion. This permits the cutting. edge to be relatively-thin and the portion ad jacent the shank to be strong enough to resist the stresses imposed thereon when said shown in Figs. 5, 6 and 7, so that the'side edges I)? and: b are slightly in advance of the remainder, The cutting edges 0 and c are cutting blade is removing metal from a plate, or the like;

Afurther object of my invention is to pro- H vide a router-bit of this character which clears the netalaway from the recess in which it is working so that the chips will {never blade when operating. tained by shaping the cutting end or face of the bit relatively to the direction of the rota tion, so that it is inclined away from the cuttingedge. L f In other words, said cutting end, or face, is tapered exteriorly toaline intersecting the longitudinal axis'of the bit.- Hence the interior recessed faces of said blades make an acute angle with the surface :upon which my router-bit is used, and tend to impinge the chips cut away from said surface against the from and to keep said surface clear of said chips. 7 v In this connection it is to be notedthat the principle of operation'of my router-bit may latter, thus to cause them to rebound there be said to be. directly opposed to'the principle employed in clearing the'chips from a wood cutting tool,,or the like; for in the latter tool the cuttingen'dis, shaped so as to be inclined to make an obtuse-angle relatively therewith and thus the chips orshavings are gouged ofl thrown up the inclined surface and-thus out ofthe cut, a Full details of construction of my: router bit are hereinafter described with reference to the accompanying drawings;

In the drawings: 7 Fig. 1 s a diagrammatic View of my improved router-bit mounted in a. rotating head and routing a flatplate;

Fig. 2 is a, larger'scaled elevation of m improved double-bladed router bit;

Fig. 3 is asimilarscaled edge elevation thereof;. p

Fig. 4 is alongitudinal section taken along the lineHofFig. 2; l

Fig. 5 is an end elevation of-said routerbita V. Fig. 6 is a cross section taken through the blade on the line 66 of Fig. 2; and

' Fig. 7 is a similar cross section taken on the line 7-7 of Fig. 2;

My improved router-bit comprisesagshank a and arblade element 5 consisting of two cutting blades 6" and having cutting edges or and 0,'at their extremities away from the shank. Each of said blades are fluted, as

clear the shavings or chips cut thereby, this feature being common in all router blades.

The I blades are virtually continuations of each other, being oppositelycurved however, and are substantially of uniform thickness across their entire. cutting'surfaces; Said:

blades, however, increase progressively in thickness towards the shank, as shown in Figs. 3 and 4,and'thus the'forwardor' concavedface cl of each of-said blades makes an acute. angle relatively to the work being I routed. As, has been brought out heretofore, the chipsroutedout of said platesare thrown downwardly, due to the inclinat on of said forward face and due to the tremendous speed to which said router-bits rotate strike with great velocity from the cut thus made and rebound away from the plate. Using a routerbit of this character requires that the operator stand behind some transparent surface but permits him to operate at great speed, for the reason that the chips never tend to clog the work. 3y making the blade relatively thin and substantially flat, I am thus able to provide a cutting edge across the entire width of both blades. Heretofore, it was common to extend the shank the entire length of the blade to obtain the necessary strength and to arrange the blade to extend sidewise therefrom. The shank is relatively thick and thus to provide sufficient clearance away from said cutting edge was backed voli at a substantial angle and all of the cutting was done with the point of said blade. This caused the point to wear away quickly-and necessitated the router being sharpened frequently. By making said blade relatively thin and substantially of uniform thickness converging toward'their lateral cutting edges,

the incurved face of each blade being inclined upwardly and outwardly from the lower cutting edge of the blade,'whereby to provide a surface forming an acute angle with the surface of the work to thereby cause the I particles out from the work to directed downwardly by such inclined suri'ace at an angle to and in a direction toward the surface being operated upon. 1

ALBERT cool-I AN; 

